Fiber guide channel devices have been known for a long time in conjunction with sliver opening devices of open-end rotor spinning machines and have been described in detail in numerous patent applications.
In open-end rotor spinning mechanisms, which are equipped with a sliver opening device of this type, a sliver intermediately stored in a spinning can is fed to a rotating opening roller, which combs the sliver into individual fibers. The combed-out individual fibers are then pneumatically supplied by means of a so-called fiber guide channel to a spinning rotor revolving at a high rotational speed in a rotor housing and continuously rotated in the rotor groove thereof onto the end of a yarn leaving the spinning rotor by means of a yarn withdrawal device. The yarn produced by the open-end rotor spinning mechanism is then wound on an associated winding device to form a cross-wound bobbin.
In open-end rotor spinning mechanisms of this type, relatively high demands are made of the configuration of the sliver opening device and the fiber guide channel devices, in particular with regard to the fiber guide channel, by means of which the individual fibers combed out by the opening roller are pneumatically transported to the spinning rotor.
The fiber guide channel devices should, for example, not only have an advantageous geometric configuration, but also be optimally designed with regard to the surface quality of their fiber guide channel.
In other words, in fiber guide channel devices of this type, flow conditions should prevail within the fiber guide channel, which ensure that the fibers are drawn, or remain drawn, during transportation and the possibility of fibers being detained in the fiber guide channel during the pneumatic fiber transportation is to be prevented.
An open end rotor spinning mechanism with a sliver opening device, in which the fiber guide channel device is configured as a separate pressure die casting, is described in German Patent Publication DE 197 12 881 A1. The pressure die casting, in this case, apart from a central fiber guide channel, has a foot part with a centering device and an annular groove to receive a sealing ring. By means of the foot part, the pressure die casting can be fixed at a precise angle and in an air-tight manner in a corresponding bore of the opening roller housing and attached by its mouth region to a central channel plate adapter receiver in the cover element of the open-end spinning mechanism. The mouth region is, in this case, also connected in an air-tight manner to the channel plate adapter receiver by means of a corresponding seal. In order to increase the service life of the components, these known fiber guide channel devices are generally also provided with a wear-protection, in other words, the pressure die castings are immersed in a nickel dispersion bath or the like.
The above-described fiber guide channel devices have proven successful in practice and are used in large piece numbers in open-end rotor spinning mechanisms.
Similar fiber guide channel devices are known from German Patent Publication DE 103 59 417 A1. These fiber guide channel devices, however, additionally have an insertion piece made of a ceramic material in the region of the entry opening of the fiber guide channel.
This insertion piece, which is non-rotatably positioned in a corresponding recess of the fiber guide channel foot, in the region of the entry opening of the fiber guide channel, forms a narrow point, which significantly reduces the internal channel cross-section, which leads to an increase in the flow speed of the transportation air flow in this region. The reduction in the internal cross-section of the fiber guide channel in the region of the entry opening has certainly proven successful especially in cotton yarns, but in other fiber materials, for example polyester or polyester mixtures, difficulties may occur upon the entry of the fibers into the fiber guide channel. Moreover, the arrangement of an insert piece of this type in the entry region of the fiber guide channel leads to a noticeable impairment of the surface quality of the fiber guide channel. In other words, narrow gaps running in the fiber transportation direction, in which individual fibers may be detained, can hardly be avoided between the fiber guide channel wall and the insert piece.
The drawback in the above-described fiber guide channel devices is also their manufacturing as zinc or aluminium pressure die castings, since, as is known, manufacturing of this type leads to permanently high tool costs. Moreover, in this method of manufacturing, the rejection quota is relative high, in particular because of the high quality demands of the surface quality in the region of the fiber guide channel.
Fiber guide channel devices, which are comparable in form, are known from German Patent Publication DE 10 2004 005 429 A1, but these fiber guide channel devices are not manufactured as zinc or aluminium pressure die castings, but produced by a special manufacturing method, which is also called MIM (Metal Injection Molding) or PIM (Powder Injection Molding) technology.
In MIM technology or PIM technology, a first oversized preform is firstly produced from a mixture of a sinterable material and a binder by injection molding, said preform being converted by releasing agents into a porous intermediate form and brought by sintering into a final form requiring little aftertreatment. The final bodies produced after the sintering can be subjected virtually without further aftertreatment in subsequent finishing processes to all conceivable heat treatment and surface treatment methods.